Adaptive brake valve cutout scheme during distributed power communication loss

ABSTRACT

In a distributed power railroad train, an apparatus for equalizing the equalizing reservoir pressure in the remote power unit and the brake pipe pressure in response to airflow into the brake pipe from the remote locomotive. With these pressures equal, the remote unit cannot charge the brake pipe while the lead unit vents the brake pipe to command a brake application at the train railcars.

[0001] This patent application is a continuation-in-part of U.S. patentapplication Ser. No. 10/271,329 filed on Oct. 15, 2002, which claims thebenefit of U.S. Provisional Patent Application No. 60/338,925, filed onDec. 10, 2001. This continuation-in-part application also claims thebenefit of U.S. Provisional Patent Application No. 60/441,948, filed onJan. 23, 2003.

FIELD OF THE INVENTION

[0002] This invention relates generally to pneumatic braking systems andmore particularly to a pneumatic braking system for a train consistcomprising a lead locomotive and one or more remote locomotives.

BACKGROUND OF THE INVENTION

[0003] One of the most critical aspects of the operation of railroadvehicles is the predictable and successful operation of the air brakesystem. However the air brake system is subjected to a variety ofdynamic effects, not only as a result of the controlled application andrelease of the brakes in response to changes in brake pipe pressure, butalso due to the varying operating conditions encountered by the train.Thus multiple operating scenarios must be considered for the successfuldesign and operation of the air brake system.

[0004] At each railcar, a control valve (typically comprising aplurality of valves and interconnecting piping) responds to locomotiveoperator-initiated changes in the brake pipe fluid pressure by applyingthe brakes (in response to a decrease in the brake pipe fluid pressure)or by releasing the brakes (in response to an increase in the brake pipefluid pressure). The fluid within the brake pipe conventionallycomprises pressurized air. The control valve at each railcar senses thedrop in brake pipe air pressure as the pressure drop propagates alongthe brake pipe. In response, at each railcar pressurized air is suppliedfrom a local railcar reservoir to the wheel brake cylinders, which inturn drive the brake shoes against the railcar wheels. The railcarreservoir is charged by supplying air from the brake pipe duringnon-braking intervals. Typically, the pressure reduction in the brakepipe for signaling a brake application is about seven to twenty-fourpsi, with a nominal steady state brake pipe pressure of about 90 psi.The braking pressure applied to the railcar wheels is proportional tothe drop in the brake pipe pressure. Thus it can be seen that the brakepipe serves to both supply pressurized air to each railcar for poweringthe brake shoes during a brake application and also serves as the mediumfor communicating brake application and release instructions to eachrailcar.

[0005] The railcar brakes can be applied in two different modes, i.e., aservice brake application or an emergency brake application. A servicebrake application involves the application of braking forces to therailcar to slow the train or bring it to a stop at a forward locationalong the track. During service brake applications the brake pipepressure is slowly reduced and the brakes are applied gradually inresponse thereto. An emergency brake application commands an immediateapplication of the railcar brakes through an immediate evacuation orventing of the brake pipe. Unfortunately, because the brake pipe runsfor several thousand yards along the length of the train, the emergencybraking evacuation does not occur instantaneously along the entirelength of the brake pipe. Thus the braking forces are not uniformlyapplied at each railcar to stop the train.

[0006] After one emergency brake application or two or three servicebrake applications, the brake pipe must be recharged to its nominaloperating pressure by supplying pressurized air from a reservoir on thelocomotive into the brake pipe. Effective subsequent brake applicationscannot be made until the recharging process has been completed.

[0007]FIG. 1 illustrates a typical prior art brake system employed by arailway freight train. In a conventional train having only a leadlocomotive, the train brake system comprises a locomotive brake systemlocated on a locomotive 100 and a set of railcar brake systems locatedon a plurality of railcars illustrated by a railcar 200. The applicationand release of braking action is controlled by an operator within thelocomotive 100, who uses a manually operated brake handle to effectbraking action. The locomotive includes an air brake control system 102for supplying air pressure to or controllably venting a pressurizedbrake pipe 101 via a brake pipe valve 120. The pressurized brake pipe101 is in fluid communication with each of the railcars 200 of the trainas shown.

[0008] The locomotive brake control system 102 comprises an air supplyinput link 111 for supplying pressurized fluid (air) through which thebrake pipe 101 is charged. A flow measuring adapter 113 is connected tothe air supply link 111 for measuring the charging rate (as adifferential pressure between the air supply an output port 116) of thebrake control system 102. The output port 116 of the flow measuringadapter 113 is connected to an input port 121 of a relay valve 117. Abi-directional port 122 of the relay valve 121 is coupled to the brakepipe 101. The relay valve 117 further includes a port 123 coupledthrough an air pressure control link 103 to an equalizing reservoir 105.The pressure control link 103 is also connected to a pressure controlvalve 107 through which the equalizing reservoir 105 is charged anddischarged in the process of a brake operation. A port 124 of the relayvalve 117 is controllably vented to the atmosphere as an exhaust port.Coupled with brake pipe 101 and air pressure control link 103 arerespective pressure measuring and display devices 131 and 133. The brakepipe gauge 131 measures the air pressure in the brake pipe 101 and theequalizing reservoir gauge 133 measures-the pressure in the equalizingreservoir 105.

[0009] The components of a railcar air brake control system 202, includea control valve 203 having a port 221 coupled to the brake pipe 101. Thecontrol valve 203 also includes a port 222 coupled to a pressure storageand reference reservoir 205. Finally, the control valve 203 includes aport 223 coupled to an air brake cylinder 231, comprising a piston 232connected to a brake shoe 233. An increase in air pressure at the port223 is fluidly communicated to the piston 232 for driving the brake shoe233 against the wheels 235 of the railcar 200. Thus the air brakecontrol system 102 of the locomotive 100 controls operation of thepneumatically operated brake shoes 233 at each of the wheels 235 of eachrailcar 200.

[0010] During train operation, the brake pipe valve 120, through whichthe components of the brake control system 102 are coupled to the brakepipe 101, is open to create a continuous brake pipe fluid path betweenthe locomotive 100 and all of the railcars 200 of the train. The brakepipe valve 120 is controlled by a brake valve cut-out valve 250, that isin turn controlled by a pilot valve 251. The pilot valve 251 can bemanually operated by the locomotive operator to close the brake pipevalve 120 when it is desired to terminate brake pipe charging or todisconnect the brake pipe 101 from the locomotive brake control system102. There are also other valves and control components (not shown inFIG. 1) that automatically terminate brake pipe charging during anemergency brake application by closing the brake pipe valve 120. Eachrailcar 200 also includes a manually-operated brake pipe valve 240, asshown in FIG. 1.

[0011] The brake system is initially pressurized by the operation of thepressure control valve 107, which controls the air supply to the controllink 103 to charge the equalizing reservoir 105 to a predeterminedpressure. The relay valve 117 is then operated to couple port 121 withthe port 122 so that air is supplied there through to the brake pipe101, charging the brake pipe 101 to the predetermined charge pressure,as established by the pressure of the equalizing reservoir 105. When thebrake pipe pressure reaches the predetermined pressure, the pressure atthe port 122 (connected to the brake pipe 101) equals the pressure atthe port 123 (connected to the equalizing reservoir 105). This conditionindicates a charged brake pipe and the fluid flow path from theequalizing reservoir 105 to the brake pipe 101 via the relay valve 117is closed.

[0012] The pressure storage and reference reservoir 205 of each railcar200 is fully charged from the brake pipe 101 through the control valve203, thereby establishing a reference pressure for maximum withdrawal ofthe piston 232 and complete release of the brakes 233 for each of therailcars 200.

[0013] To brake the railcars 200, the train operator operates thepressure control valve 107 using the braking handle in the locomotivecab. This operation causes a partial venting of the air pressure controllink 103 through the exhaust port of the pressure control valve 107,reducing the pressure within the equalizing reservoir 105. This pressurereduction is sensed by the relay valve 117 at the port 123. In turn, thepressure reduction causes the bi-directional port 122 to be coupled tothe exhaust port 124, thereby exhausting the brake pipe 101 to theatmosphere. The venting of the brake pipe 101 continues until thepressure within the brake pipe 101 equals the pressure of equalizingreservoir 105.

[0014] As the pressure in the brake pipe 101 falls, the control valve203 in each of the cars 200 senses the pressure reduction by comparingthe brake pipe pressure with the pressure storage and referencereservoir pressure. This pressure reduction causes a correspondingincrease in the air pressure applied to the brake cylinder 231 from theport 223, resulting in an application of the brake shoes 233 against thewheels 235 in proportion to the sensed pressure reduction in the brakepipe 101.

[0015] Further pressure reductions in the equalizing reservoir 105 bythe train operator produce corresponding pressure reductions in thebrake pipe 101 and, corresponding additional braking effort by the brakeshoes 233 in each of the railcars 200. In summary, the intendedoperation of the brake system in the cars 200 and specifically thebraking effort applied in each of the cars 200, is proportional to thereduction in pressure in the equalizing reservoir 105 within thelocomotive 100.

[0016] When the locomotive operator desires to release the train carbrakes, she operates the pressure control valve 107 via the brakinghandle, to effectuate a recharging of the air brake system 102. Therecharging is accomplished by bringing the pressure within theequalizing reservoir 105 back to its fully charged state by supplyingpressurized air via the flow measuring adapter 113 and the relay valve117. With the equalizing reservoir 105 recharged, there is again apressure differential (but opposite in sign to the previous pressuredrop in the pressure line 103) between the ports 122 and 123 of therelay valve 117 that causes the brake pipe 101 to be charged withpressurized air from air supply 111 through the flow measuring adapter113 and the relay valve 117. The brake pipe pressure increase is sensedby the control valve 203 in each of the railcars 200 to cause the brakeshoes 233 to be released by the action of the brake cylinder 231.

[0017] Distributed power train operation supplies motive power from alead locomotive and one or more remote locomotives spaced apart from thelead unit in the train consist. Distributed train operation may bepreferable for long train consists to improve train handling andperformance. Each lead and remote locomotive includes an air brakecontrol system, such as the air brake control system 102 discussedabove, and a communications system for exchanging information betweenthe lead and the remote units. Conventionally the communications systemcomprises a radio frequency link and the necessary receiving andtransmitting equipment at each of the lead and the remote units.

[0018] The description of the present invention below with respect tothe brake control system of a remote locomotive in a distributed powertrain consist refers to the same brake control system components anduses the same reference characters as described above in conjunctionwith the brake control system of the lead locomotive. Specific mentionwill be made if the reference pertains only to the lead or only to theremote locomotive.

[0019] On distributed power trains equipped with UIC (UnionInternationale de Chemins Fer) wagon braking equipment, braking isaccomplished by venting the brake pipe 101 at both the lead and remotelocomotives, thus accelerating the brake pipe venting and theapplication of the brakes at each railcar, especially for those railcarsnear the end of the train. Brake pipe venting at only the lead unitrequires propagation of the brake pipe pressure reduction along thelength of the train, thus slowing brake applications at railcars distantfrom the lead unit. For a distributed power train with an operativecommunications link between the lead and remote units, when the trainoperator commands a brake application by operation of the brake handleat the lead unit, a brake application command is transmitted to eachremote unit over the radio frequency communications link. In response,each remote unit also vents the brake pipe through its respective relayvalve 117. Thus braking actions at the remote locomotives follow thebraking actions of the lead unit in response to signals transmitted bythe communications system. As a result, the entire brake pipe is ventedfaster than if the venting occurred only at the lead locomotive. A brakerelease initiated at the lead unit is also communicated over the radiofrequency link to the remote units so that the brake pipe 101 isrecharged from all locomotives.

[0020] If the communications system is inoperative or if thecommunications link between the lead unit and the remote units isdisrupted (for example, if line-of-sight directivity is lost due totrack topology or an interfering object), when the lead operator makes abrake application the remote locomotives will not receive the brakeapplication command via the communications system. Thus the brakeapplication is executed by venting the brake pipe only at the leadlocomotive, resulting in a slower brake application at all the railcars.

[0021] It is known that leaks can develop in the brake pipe, causingunwanted pressure reductions. Thus in one operational mode for adistributed power train, the remote units (and the lead unit)continually charge the brake pipe 101 when the pressure falls below anominal value (i.e., whenever a brake application is not in progress). Aremote unit senses the brake pipe pressure via the relay valve 117, thatcompares the equalizing reservoir pressure with the brake pipe pressure.Whenever the brake pipe pressure is less than the equalizing reservoirpressure, the brake pipe 101 is charged from the air supply 111 via therelay valve 117 of the remote unit. However, a remote unit should notrecharge the brake pipe when a brake application has been initiated atthe lead unit.

[0022] A dangerous scenario can develop if a brake application commandtransmitted over the communications link from the lead unit does notreach the remote locomotive while the latter is monitoring andrecharging the brake pipe to compensate for pressure reductions causedby leaks within the brake pipe 101. Typically, the recharging process isinitiated if the brake pipe pressure falls below a nominal predeterminedvalue. In this situation the remote locomotive continues to recharge thebrake pipe 101 as the lead unit is venting the brake pipe to signal abrake application to the railcars 200. This situation can causedangerously high in-train forces to develop.

[0023] One prior art technique for avoiding this scenario is toautomatically close the brake pipe valve 120 of the remote unit whenevercommunications is lost between the lead and the remote locomotive units.With the brake pipe valve 120 closed, the remote units cannot recharge(nor vent) the brake pipe 101. Thus all brake signaling (both brakeapplications and brake releases) over the brake pipe 101 is initiatedfrom the lead unit. Although under this condition the remote locomotivescannot assist with the brake pipe venting to accelerate brakeapplications at the railcars 200, the remote locomotives also cannoterroneously recharge the brake pipe while the lead unit is venting it.

[0024] The prior art LOCOTROL® distributed power communications system(available from the General Electric Company of Schenectady, N.Y.)incorporates a variant of the technique described above by including abrake pipe flow sensing function at each remote locomotive in adistributed power train. A flow sensor, such as the flow measuringadapter 113 as depicted in FIG. 1, is included in the brake pipecharging path at each remote unit to detect air flow from the air supplythrough the relay valve 117 to the brake pipe 101. If the flow rate(which is determined by a differential pressure) exceeds a predeterminedvalue, a brake application is declared. That is, the brake pipe pressurehas fallen to a value consistent with a brake application (which wouldhave been initiated from the lead locomotive). If concurrently thecommunications system is inoperative, then in response to thesimultaneous occurrence of these two events, the remote unit brake pipevalve 120 is commanded to a cut-out or closed position. Proper executionof the command closes the remote unit brake pipe valve 120. As a result,the brake application initiated by the venting of the brake pipe at thelead unit cannot be countered by pressurizing of the brake pipe at theremote unit.

[0025] If the command to cut-out or close the brake pipe valve 120 isnot property executed, then the brake valve at the remote unit remainsopen. There are several possible causes for this scenario, including afailure of the brake valve cut-out valve 250 (i.e., the valve thatdrives the brake pipe valve into a cut-off or closed configuration), afailure of the pilot valve 251 that drives the brake valve cut-outvalve, or a brake pipe valve 120 stuck in the open position. Thus, ifthe brake pipe valve is not closed or cut-out as commanded, and during acommunications system failure the lead unit issues a brake application,then the remote units continue to supply brake pipe recharging pressurewhile the lead unit is venting the brake pipe to apply the railcarbrakes. This sets up an undesirable situation where the front railcarsexperience maximum braking and rear railcars experience minimum or nobraking action. The net result is that the rear of the train can runinto the front of the train, causing high in-train forces and possiblederailment.

BRIEF SUMMARY OF THE INVENTION

[0026] An apparatus and method for a railroad train comprising afluid-carrying brake pipe for connecting a lead locomotive, one or moreremote locomotives, and a plurality of railcars. The train furthercomprises a communications system for communicating information betweenthe lead and the remote locomotives. Each railcar comprises a brakeresponse system responsive to the brake pipe fluid pressure, ascontrolled by a brake control system in the lead and the remotelocomotives. Each of the lead and remote locomotives is coupled to thebrake pipe via a brake pipe valve and comprises an equalizing reservoirin fluid communication with the brake pipe.

[0027] A flow detector at the remote locomotive senses fluid flowbetween the remote locomotive and the brake pipe and provides a flowsignal indicative of unexpected fluid flow in the brake pipe. Thecommunications system provides a status signal indicative of itsoperability. A controller determines the status of the brake controlsystem of the remote locomotive. If the brake system is in a releasedstate, in response to the unexpected fluid flow and the status signal,the controller reduces the equalizing reservoir pressure to apredetermined value. Thereafter the controller controls the equalizingreservoir pressure in response to the flow signal, such that the brakepipe pressure at the remote locomotive is responsive to the equalizingreservoir pressure at the remote locomotive.

BRIEF DESCRIPTION OF THE DRAWINGS

[0028] The present invention can be more easily understood and thefurther advantages and uses thereof more readily apparent, whenconsidered in view of the following detailed description when read inconjunction with the following figures, wherein:

[0029]FIG. 1 is a block diagram of a prior art train braking systemaccording to the teachings of the present invention.

[0030]FIGS. 2 and 3 are block diagrams of a train braking systemaccording to the teachings of the present invention.

[0031]FIGS. 4 through 7 are flow charts illustrating the stepsassociated with the train braking system according to variousembodiments of the present invention.

[0032] In accordance with common practice, the various describedfeatures are not drawn to scale, but are drawn to emphasize specificfeatures relevant to the invention. Reference characters denote likeelements throughout the figures and text.

DETAILED DESCRIPTION OF THE INVENTION

[0033] Before describing in detail the particular method and apparatusfor the control of railroad train braking systems in accordance with thepresent invention, it should be observed that the present inventionresides primarily in a novel combination of hardware and softwareelements related to said method and apparatus. Accordingly, the hardwareand software elements have been represented by conventional elements inthe drawings, showing only those specific details that are pertinent tothe present invention, so as not to obscure the disclosure withstructural details that will be readily apparent to those skilled in theart having the benefit of the description herein.

[0034] As applied to distributed power train operation, the presentinvention detects failures in the brake valve cut-out circuit at aremote locomotive unit and the execution of remedial measures to ensurethat a brake application (i.e., venting of the brake pipe 101) initiatedat the lead locomotive is not countered by charging of the brake pipe101 at a remote unit. Thus the teachings of the present ensure that abrake application command issued by a lead locomotive is not counteredby brake pipe recharging at a remote locomotive.

[0035] Turning to FIG. 2, the locomotive 100 of the prior art isaugmented with a controller 300, responsive to the flow measuringadapter 113, for controlling the equalizing reservoir pressure via alink 301, and a communications system 302. To execute the teachings ofthe present invention, the controller 300 is located in a remotelocomotive and can optionally be operative in the lead locomotive,although this is not required as the controller 300 functions to controlcertain air brake components of the remote unit to avoid the potentiallydestructive braking scenarios described above. The communications system302 comprises the various elements as discussed above that providecommunications between the remote power unit and the lead power unit.

[0036] Under normal operating conditions, the brake pipe 101 is chargedfrom the remote unit whenever the remote unit detects a drop in thebrake pipe pressure as determined by the remote unit relay valve 117. Asdescribed above, this mode is operative to overcome the effects of brakepipe leaks. The brake pipe valve 120 of a remote power unit can becommanded out (also referred to as commanded closed or cut-off) by amessage sent from the lead unit over the communications channel to thecommunications system 302 of the remote unit. The command is processedthrough the controller 300 to electrically actuate the pilot valve 251,thereby supplying air pressure to the brake valve cut-out valve 250,that in turn closes the brake pipe valve 120. When the brake pipe valve120 is cut-off or cut-out, the airflow from the remote unit into thebrake pipe 101 falls to zero. Thus the brake pipe 101 cannot be charged(or vented) from the remote unit.

[0037] If there is a failure in the brake valve cut-out circuit (thatis, the components engaged in the operation of cutting off or closingthe brake valve at the remote unit) the fluid path from the remote unitto the brake pipe 101 remains open. The flow of charging air into thebrake pipe 101 from the remote unit is detected by the flow measuringadapter 113 at the remote unit.

[0038] In one embodiment of the present invention, whenever there is aninterruption in the communications system between the lead and theremote locomotives of a distributed power train consist, the remote unittakes control of its brake valve 120. Specifically, a signal indicatingthat the communications system is not operative is provided by thecommunications system 302 to the controller 300. In response, thecontroller 300 commands the brake valve 120 on the remote unit to closeby supplying an electrical signal to the pilot valve 251, which in turnsupplies air pressure to the brake valve cut-out valve 250, which inturn closes the brake pipe valve 120. If this command is properlyexecuted, the flow measuring adapter 113 at the remote unit senses noairflow into the brake pipe 101 from the air supply and provides arepresentative signal to the controller 300.

[0039] If the command is not properly executed, then a failure hasoccurred in the brake valve cut-out circuit and the flow measuringadapter 113 detects airflow into the brake pipe 101 whenever the remoteunit equalizing reservoir pressure is not equal to the brake pipepressure. In response, a representative signal is provided from the flowmeasuring adapter 113 to the controller 300. The failure of the brakevalve cut-out circuit can be caused by any one or more of the following:the remote brake valve 120 is inoperable or stuck in the open positionand cannot be closed by the brake valve cut-out valve 250, the brakevalve cut-out valve 250 did not operate properly, or the pilot valve 251did not function properly. Responsive to a brake valve cut-out circuitfailure, the lead locomotive is alerted immediately if possible, orlater when communications service is restored, by a signal generated bythe controller 300 and transmitted to the lead locomotive via thecommunications system 302. In response to this condition, in oneembodiment the lead locomotive commands the train to an emergencyoperational mode.

[0040] The present invention teaches an apparatus and method foravoiding brake pipe recharging from the remote unit under conditionswhen the brake pipe valve 120 has been commanded closed, but remainsopen. The present invention is thus operative whenever the flowmeasuring adapter 113 detects airflow into the brake pipe 101 when thebrake pipe valve 120 has been commanded closed. For example, the brakepipe valve 120 is commanded closed during a communications systeminterruption as mentioned above. In response to a command to close thebrake pipe valve 120 and the detection of airflow into the brake pipe101, the controller 300 lowers the pressure of the remote unitequalizing reservoir 105 via the link 301 (referred to as a pressurebleed down) until the airflow detected by the flow measuring adapter 113reaches zero. In one embodiment the equalizing reservoir pressure isreduced in small increments until the pressure equilibrium is reached.Once the equalizing reservoir pressure and the brake pipe pressure areequal, the remote unit cannot recharge the brake pipe 101, since therecharging process is based on a pressure differential between theequalizing reservoir 105 and the brake pipe 101. Advantageously, if theremote unit cannot charge the brake pipe 101, then brake applicationsinitiated at the lead unit will not be countered by pressure increasesat the remote unit, which is a possible scenario according to the priorart distributed power train system.

[0041] The process of equalizing the brake pipe pressure and theequalizing reservoir pressure continues so long as airflow is sensed bythe flow measuring adapter 113. Thus if the lead locomotive unitinitiates a second brake application by a further reduction in the brakepipe pressure, when the pressure reduction propagates to the remote unitthe flow measuring adapter 113 detects airflow due to the pressuredifferential between the remote unit equalizing reservoir 105 and thebrake pipe 101. In response the controller 300 initiates the equalizingreservoir bleed-down process until the airflow falls to zero. Reductionof the equalizing reservoir pressure continues, as needed, to follow thebrake pipe pressure reductions initiated at the lead unit, thusmaintaining zero airflow into the brake pipe 101 at the remote unit.

[0042] In addition to initiation of the method according to the presentinvention whenever the remote unit brake valve has been commandedclosed, the method can also be activated under any conditions when theflow measuring adapter 113 detects airflow into the brake pipe 101during a brake application. For instance, in another embodiment, thelead and remote units can operate on the basis of a time-based ortriggering-event braking algorithm, such that at predetermined times orin response to predetermined triggering events (a trackside actuator,for example) the train brakes are applied. If the remote unit flowmeasuring adapter 113 detects airflow into the brake pipe 101 at theremote unit when the brakes should be applied, then in response thereto,under control of the controller 300, the equalizing reservoir pressureis reduced, as discussed above, so that the lead unit brakingapplication can propagate along the brake pipe 101. As in the scenariodiscussed above, this technique avoids a situation where the lead unitis commanding a brake application while the remote unit is pressurizingthe brake pipe 101.

[0043] Thus, according to the teachings of the present invention, in asituation where there has been a failure to cut out or close the brakepipe valve 120 at the remote unit, such that the brake pipe 101 can becharged from the remote unit when the operator in the lead unit makes abrake application, the remote unit detects airflow into the brake pipeand in response thereto the pressure in the equalizing reservoir isreduced until the airflow drops to about zero, such that the pressure ofthe equalizing reservoir in the remote unit is about equal to the brakepipe pressure. Note that since the brake pipe pressure is also equal tothe equalizing reservoir pressure in the lead unit, then the remote unitequalizing reservoir pressure is about equal to the lead unit equalizingreservoir pressure. In this way, the brake applications originated atthe lead locomotive are permitted to propagate throughout the train.

[0044] In another embodiment of the present invention, as illustrated inFIG. 3, in lieu of the flow measuring adapter 113 detecting air flowfrom the air supply into the brake pipe 101, the controller 300 measuresthe brake pipe pressure (via the brake pipe gauge 131) and theequalizing reservoir pressure (via the equalizing reservoir gauge 133).If there is a difference between these two pressure values during aperiod when the brake pipe valve 120 has been commanded closed, then theequalizing reservoir 105 is bled until the two pressures are equal, atwhich point the equalizing reservoir 105 is unable to charge the brakepipe 101 and counter a brake application signaled by the lead locomotiveunit. In another embodiment, in lieu of the flow measuring adapter 113,a flow measuring device (not shown) can be disposed within the brakepipe at the remote unit for detecting fluid flow into the brake pipefrom the remote unit.

[0045] In yet another embodiment, rather than bleeding down theequalizing reservoir as described above in various embodiments, theequalizing reservoir 105 can be evacuated through the pressure controlvalve 107 under control of the controller 300. Once evacuated, theequalizing reservoir 105 is unable to charge the brake pipe 101 and thuscannot counter a brake application signaled by the lead locomotive unit.

[0046]FIG. 4 is a flow chart depicting the method according to thepresent invention for controlling brake pipe charging and venting at theremote locomotives of a distributed power train consist. A decision step350 determines whether the communications system between the remotelocomotive and the lead locomotive is operative. There are several knowntechniques for accomplishing this, including transmitting a test signalat regular intervals between the lead and remote units and measuring oneor more signal metrics (e.g., signal-to-noise ratio, bit error rate) atthe receiving end. If the communications system is functioning properly,when brake applications are initiated at the lead unit a braking signalis sent to and received at the remote units. In response the remoteunits also initiate a brake application by venting of the brake pipe. Ifthe communications system is not operating properly, brake applicationsat the lead unit will not be assisted by brake applications at theremote units, and worse, the remote unit may recharge the brake pipewhile the lead unit is lowering the brake pipe pressure to initiate abrake application. Further, as discussed above, there are conditions,other than a failure of the communications system, for which the processof FIG. 2 is operative. In those cases, the decision step 350 isreplaced with a decision step to determine whether any such othercondition exists. One example of such a condition is whether a trackactuator has commanded a brake application.

[0047] If the result of the decision step 350 is negative thecommunications system is operating properly and the process loopsperiodically back through the decision step 350. If the response ispositive, the process proceeds to a step 352 where the brake pipe valve120 is commanded closed. As described above, this can be accomplished byoperation of the pilot valve 251, which in turn operates the brake valvecut-out valve 250 for closing the brake pipe valve 120. Following thestep 352, a decision step 354 determines whether the flow measuringadapter 113 detects airflow from the air supply into the brake pipe 101.If no airflow is detected then the brake valve 120 is apparently closedand the process returns to the decision step 350. In lieu of an flowdetector such as the flow measuring adapter 113, the present inventioncontemplates use of any detector that is capable of determining theposition of the brake pipe valve or whether the brake valve is open orclosed, such as a valve position detector.

[0048] If the result of the decision step 354 is affirmative, then thebrake valve has failed to close in response to the command at the step352. This failure is reported to the lead unit at a step 356. Note thatthis step is not functionally required for successful implementation ofthe present invention, but is suggested so the train operator is madeaware of the failed attempt to close the brake pipe valve.

[0049] As described above, if the brake pipe valve at a remote unit isopen while the lead unit attempts to vent the brake pipe to command abrake application, then the railcars beyond the remote unit may not seethe declining brake pipe pressure as the remote unit will attempt torecharge the brake pipe as the lead unit attempts to vent it. Theserailcars will thus not engage their brakes. To resolve this problem, inone embodiment (not illustrated in FIG. 4) the train goes into anemergency operating mode in response to the failure of the brake valveto close. In the FIG. 4 embodiment, the equalizing reservoir pressure atthe remote unit is reduced at a step 358, with the objective ofattaining an equalizing reservoir pressure equal to the brake pipepressure. At a decision step 360 a determination is made as to whetherthe brake pipe valve 120 is still commanded closed. An affirmativeresponse returns the process to the decision step 354 for determiningwhether airflow is detected by the flow measuring adapter 113. As longas airflow is detected, the equalizing reservoir pressure is reduced atthe step 358. Thus after several passes through the loop comprising thedecision step 354, the step 356 (once the lead unit has been advised ofthe failure of the brake pipe valve to close, this step can be bypassedon subsequent passes through the loop), the step 358 and the decisionstep 360, the equalizing reservoir pressure will eventually equal thebrake pipe pressure and the result from the decision step 354 will turnaffirmative. By equalizing the pressure of the remote unit equalizingreservoir and the brake pipe, the remote unit cannot charge the brakepipe while the lead unit is attempting to vent it.

[0050]FIG. 5 illustrates another method according to the teachings ofthe present invention. Whenever brake pipe charging is permitted fromthe remote unit, as represented by a step 380, the brake pipe pressureis determined at step 382. If a brake application is in process, asdetermined by a falling brake pipe pressure at the step 382, then brakepipe charging is terminated (see a step 386) at the remote unit suchthat the remote cannot charge the brake pipe while the lead unit isattempting to vent it. If no brake application has been determined, theprocess returns to the step 380.

[0051] According to the embodiment of FIG. 6, the equalizing reservoirpressure is determined at a step 390 and the brake pipe pressure isdetermined at a step 392. If the equalizing reservoir pressure exceedsthe brake pipe pressure during a predetermined operating condition, asindicated at a step 394, then the equalizing reservoir pressure isreduced.

[0052]FIG. 7 illustrates a flow chart for yet another embodiment of thepresent invention. In this embodiment, during communicationsinterruptions between the lead locomotive and the remote locomotives,the latter attempts to follow the braking action initiated at the leadlocomotive to assist with the propagation of brake application andrelease commands at the remote unit. Note that in certain embodimentsdiscussed above, the remote unit is cut-off from the brake pipe 101 (byclosure of the brake pipe valve 120) during communications systemsfailures, and thus cannot assist with the brake pipe venting during abrake application and cannot assist with brake pipe recharging followingbraking action.

[0053] Beginning at a step 400, when the flow measuring adapter 113detects unexpected air flow within the brake pipe 101, the process movesto a step 402. As discussed above, in a distributed power train controlsystem, the lead unit and the remote unit communicate over acommunications link. Brake application and brake release commands aresent over the link from the lead unit for execution at the remote unit.Thus, an unexpected air flow could occur when the brake pipe flow sensedby the flow measuring adapter 113 is inconsistent with a brake releaseor a brake application command transmitted from the lead unit to theremote units. For example, when airflow is detected into the brake pipefollowing a brake application command. Unexpected air flow can alsooccur in response to fluctuations in the equalizing reservoir pressure(during cycling of a compressor (not shown in the Figures) thatmaintains the reservoir pressure, air dryer exhausts, etc.) orfluctuations in the brake pipe pressure (e.g., leakage fluctuations inthe brake pipe 101 due to stretch leakage caused when the railcar hosesthat interconnect the brake pipe segments associated with each railcarstretch and compress as the railcar travels around a curve).

[0054] In response to the detection of unexpected air flow, the processcontinues to a decision step 402 where a determination is made regardingthe operability of the communications link between the remote locomotiveand the lead locomotive. During normal operation of the communicationssystem, in one embodiment the lead and the remote units send test orinformation messages to each other about every 20 seconds. If about 45seconds elapses during which the remote locomotive does not receive atransmission from the lead unit, then a communication system failure isdeclared. Thus the decision step 402 determines whether such acommunications systems failure has been declared. The process moves to astep 410 if the result of the decision step 402 is affirmative.

[0055] If such a failure has not been declared, then the process movesfrom the decision step 402 to a step 404, where the remote unittransmits a communications test message to the lead unit. If the leadunit responds to the test message, then the result at the decision step406 is affirmative and the system returns to normal operation.

[0056] If the lead unit fails to respond to the remote unit, then theresult from the decision step 406 is negative, that is, a communicationssystem failure is declared and the process moves to the step 410.

[0057] At the step 410 the process enters an adaptive remote brakeapplication sequence, where the remote locomotive is switched to an idlestate. In an idle state the remote locomotive supplies no motive powerto the train consist. In this mode, brake applications at the lead unitwill not be countered by the application of motive power at the remoteunits.

[0058] At a decision step 412, it is determined whether the remotelocomotive was in a released brake state (i.e., the brakes are notapplied at the railcars 200) immediately prior to detection of thecommunications link failure. If the remote was in a released brake state(i.e., the remote unit was not venting the brake pipe to signal a brakeapplication), the pressure of the equalizing reservoir 105 is reduced(by venting through the controller 300 through the link 301. In oneembodiment the pressure is reduced to a pressure representative of aminimal service brake application. This process is depicted at a step414 of FIG. 7. If the remote unit was not in a released brake state, theprocess continues from the decision step 412 directly to a decision step416, bypassing the step 414. With the equalizing reservoir pressure at aservice brake application value, the remote unit is unable to charge thebrake pipe 101 (i.e., in the event the lead unit is venting the brakepipe 101). In lieu of venting the equalizing reservoir 105 through thecontroller 300 as described above, the controller 300 provides a controlsignal to the pressure control valve 103 for incrementally venting theequalizing reservoir there through.

[0059] Following either the decision step 412 or the equalizingreservoir pressure reduction step 414, the process continues to thedecision step 416. The flow measuring adapter 113 (see FIG. 3) monitorsflow into the brake pipe to determine whether the flow into the brakepipe 101 has dropped to zero. As described below, the flow monitoringcontinues for a time period during which brake pipe pressureequalization (and thus zero flow) would be expected. If the flowmeasuring adapter 113 senses air flow responsive to a falling brake pipepressure, the remote unit equalizing reservoir pressure is incrementallyreduced at a step 418, thus aiding in the brake application processinitiated at the lead unit. The path comprising the decision step 416and the step 418 is repeatedly traversed (and the equalizing reservoirpressure decreased during each traversal through the step 418) untilzero flow is detected by the flow measuring adapter 113, after which theprocess continues to a decision step 420.

[0060] At the decision step 420, it is determined whether the flow timeris running. On the first pass through the decision step 420, the processmoves to a step 422 where the flow timer is started. The process thenloops back through the decision step 416. If the air flow remains atabout zero, the process continues from the decision step 416 to thedecision step 420 and then to a decision step 424. This decision step424 determines whether the flow timer has reached a predeterminedmaximum value. If the flow timer has not reached that maximum value, theprocess loops back to the input of the decision step 416. Once the flowtimer is greater than or equal to the predetermined time (or in anotherembodiment greater than the predetermined time), the process moves to astep 426 where the brake pipe valve 120 on the remote unit is cut out orclosed. In one embodiment, the predetermined time associated with thedecision step 424 is about one minute. Thus the flow timer establishes amaximum time during which the flow is monitored. In the event the flowhas remained at about zero for the timing interval, then it is assumedthat the brake pipe charging or venting event has ceased and normaloperation of the distributed power communication system should bere-established. Following the step 426, the distributed power systemexecutes through a series of known process steps to reestablish thecommunications link between the lead unit and the remote unit, afterwhich the brake pipe valve 252 is opened. Thus, the remote unit has beenreturned to its operational state prior to the detection of unexpectedairflow at the step 400.

[0061] While the invention has been described with reference topreferred embodiments, it will be understood by those skilled in the artthat various changes may be made and equivalent elements may besubstituted for elements thereof without departing from the scope of thepresent invention. The scope of the present invention further includesany combination of the elements from the various embodiments set forthherein. In addition, modifications may be made to adapt a particularsituation to the teachings of the present invention without departingfrom its essential scope. Therefore, it is intended that the inventionnot be limited to the particular embodiment disclosed as the best modecontemplated for carrying out this invention, but that the inventionwill include all embodiments falling within the scope of the appendedclaims.

What is claimed is:
 1. An apparatus for a railroad train wherein afluid-carrying brake pipe connects a lead locomotive, a remotelocomotive and a plurality of railcars, wherein a communications systemcommunicates information between the lead locomotive and the remotelocomotive, wherein each one of the plurality of railcars comprises abrake response system responsive to the brake pipe fluid pressure, andwherein the lead locomotive and the remote locomotive comprise a brakecontrol system in fluid communication with the brake pipe via a brakepipe valve, wherein the brake control system controls the brake pipefluid pressure, the apparatus comprising: at the remote locomotive: aflow detector for sensing fluid flow from the remote locomotive into thebrake pipe, and for providing a flow signal representative of detectedfluid flow, and further for providing an indication of unexpected fluidflow; wherein the communications system provides a status signalindicative of the operability of the communications system; anequalizing reservoir in fluid communication with the brake pipe; acontroller, wherein in response to the indication of unexpected fluidflow and the status signal the controller initiates a reduction in theequalizing reservoir pressure, and wherein the controller continues toreduce the equalizing reservoir pressure in response to the flow signal.2. The apparatus of claim 1 wherein braking system commands aretransmitted from the lead locomotive to the remote locomotive over thecommunications system, and wherein the unexpected fluid flow comprises afluid flow inconsistent with the last braking system command.
 3. Theapparatus of claim 1 wherein the status signal indicative of theoperability of the communications system indicates an inoperablecommunications system.
 4. The apparatus of claim 1 wherein theoperability of the communications system is determined by sending asignal from the remote locomotive to the lead locomotive and receiving aresponse from the lead locomotive.
 5. The apparatus of claim 1 whereinthe communications system is inoperable if the remote locomotive failsto receive a signal from the lead locomotive during a predeterminedinterval.
 6. The apparatus of claim 1 wherein the controller determinesthe status of the brake control system of the remote locomotive, whereinif the brake control system status is released, then in response to theindication of unexpected fluid flow and the status signal the controllerreduces the equalizing reservoir pressure to a predetermined pressure,after which the controller continues to reduce the equalizing reservoirpressure in response to the flow signal.
 7. The apparatus of claim 6wherein the predetermined pressure represents a service brakeapplication.
 8. The apparatus of claim 1 wherein the controller controlsthe equalizing reservoir pressure in response to the flow signal untilthe flow signal indicates substantially no flow from the remotelocomotive into the brake pipe.
 9. The apparatus of claim 8 wherein whenthe flow signal indicates substantially no flow for a predetermined timethe brake pipe valve at the remote locomotive is closed.
 10. Theapparatus of claim 9 wherein the predetermined time is about one minute.11. The apparatus of claim 1 wherein in response to the indication ofunexpected fluid flow and the status signal, the remote locomotive ispowered to an idle state wherein the remote locomotive provides nomotive power to the railroad train.
 12. A method for controlling arailroad train comprising a fluid-carrying brake pipe connecting a leadlocomotive, a remote locomotive and a plurality of railcars, furthercomprising a communications system for communicating information betweenthe lead locomotive and the remote locomotive, wherein each one of theplurality of railcars comprises a brake response system responsive tothe brake pipe fluid pressure, and wherein the lead locomotive and theremote locomotive comprise a brake control system in fluid communicationwith the brake pipe via a brake pipe valve, wherein the brake controlsystem controls the brake pipe fluid pressure, the method comprising: atthe remote locomotive: detecting fluid flow from the remote locomotiveinto the brake pipe, and in response thereto providing a flow signalrepresentative of detected fluid flow, and further providing anindication of unexpected fluid flow; determining the operability of thecommunications system and in response thereto providing a status signalrepresentative of the communications system status; and reducing thebrake pipe fluid pressure in response to the indication of unexpectedfluid flow, the status signal and the flow signal.
 13. The method ofclaim 12 further comprising transmitting braking system commands fromthe lead locomotive to the remote locomotive over the communicationssystem, and wherein the unexpected fluid flow comprises a fluid flowinconsistent with the last braking system command.
 14. The method ofclaim 12 further comprising determining the status of the brake controlsystem of the remote locomotive, wherein if the brake control systemstatus is released, then the step of reducing the brake pipe fluidpressure comprises reducing the brake pipe pressure to a predeterminedpressure, after which the reduction in brake pipe fluid pressurecontinues in response to the flow signal.
 15. The method of claim 14wherein the predetermined pressure represents a service brakeapplication.
 16. The method of claim 12 wherein the step of reducing thebrake pipe fluid pressure comprises reducing the brake pipe fluidpressure until the flow signal indicates substantially no flow from theremote locomotive into the brake pipe.
 17. The method of claim 16further comprising determining if the flow signal indicatessubstantially no flow for a predetermined time and closing the brakepipe valve at the remote locomotive after the predetermined time. 18.The method of claim 17 wherein the predetermined time is about oneminute.
 19. The method of claim 12 further comprising powering theremote locomotive to an idle state in response to the indication ofunexpected fluid flow and the status signal.